package com.loaderman.countdowntimerdemo;
 
import android.os.Bundle;
import android.os.CountDownTimer;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;
 
public class MainActivity extends AppCompatActivity {
 
  private TextView tvTime;
 
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    tvTime = (TextView) findViewById(R.id.tv_time);
    tvTime.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        new countDownTimer<TextView>(tvTime);
      }
    });
  }
  public class countDownTimer<T> extends CountDownTimer {
    private TextView mTextView;
 
    public countDownTimer(T text) {
      super(60000,1000);
      this.mTextView = ((TextView)text);
      mTextView.setClickable(false);
      start();
    }
 
    /**
     * start后开始执行的方法，按照间隔时间执行一次
     * @param millisUntilFinished
     */
    @Override
    public void onTick(long millisUntilFinished) {
      mTextView.setText(String.format("%s秒",millisUntilFinished/1000));
    }
 
    /**
     * 时间结束时调用的方法
     */
    @Override
    public void onFinish() {
      mTextView.setText("获取验证码");
      mTextView.setClickable(true);
    }
  }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:id="@+id/activity_main"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:gravity="center"
  tools:context="com.loaderman.countdowntimerdemo.MainActivity">
  <TextView
    android:textColor="#F00"
    android:textSize="18sp"
    android:id="@+id/tv_time"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="开始倒计时"/>
</RelativeLayout>